This invention relates to the distribution of a plastic of the butyl rubber type, particularly for the extrusion of the bead intended to serve as a seal and interlayer in multilayer glass sheets, hereinafter referred to as multiple glazings, and it relates more particularly to the preparation of said plastic and its routing from a tank where it is hard, viscous and at a relatively low temperature to an extrusion nozzle, optionally mobile in relation to the tank, where it should have a viscosity and hardness much lower than it had initially in the tank, and a higher temperature.
It is known from French Pat. No. 2 211 413 how to prepare a plastic of the butyl rubber type for the extrusion of a bead intended to be deposited on a glass sheet to make a multiple glazing, to work from small amounts of material, that can be easily and quickly heated, to obtain satisfactory characteristics of viscosity and hardness, on the one hand for the extrusion of the bead, on the other hand for the bonding of the bead thus extruded to a glass sheet. In addition, according to this prior patent, the extrusion unit is stationary and the glass sheets move to receive the extruded bead successively along all their edges.
This prior technique is satisfactory. However to increase the rates of production on the one hand, and to increase the dimensions of the extruded beads on the other hand, it has been known to avoid working from small amounts of material, which would necessitate too-frequent stops for refeeding, but from large amounts of material, particularly directly from the drums of raw material delivered by the supplier.
These large amounts are more difficult to heat than small amounts, which restricts the deliveries and the rates while, on the contrary, it is desired to increase said deliveries and said rates.
To obtain at the output of the extrusion nozzle a suitable material, with the desired delivery, at the suitable temperature, different stages for preparing the material therefore have to be created, which necessitates circuits to feed these various stages.
Further, it has also been considered to use a technique for placing the bead on the glass sheets in which the nozzle supplying the bead would no longer be stationary, but would move, at least in one direction. Therefore, the circuits conducting raw material up to the nozzle necessarily have a relatively great length and cannot be stationary. To convey the material along these circuits, it is, on the one hand, as already stated, difficult to heat it sufficiently to lower its viscosity, on the other hand neither is it desirable to overheat it, so as not to degrade it. It is therefore, necessary during the various stages for preparing the plastic to combine a moderate heating and a pressurizing.
It is known how to convey plastics in hoses, optionally cladded, but such material is, at certain times in its path, at pressures greater than 300 bars and at temperatures greater than 100.degree. C. and the known holes are incapable of resisting this temperature and this pressure at the same time.